Cancer is one of the deadliest illnesses in the United States. It accounts for nearly 600,000 deaths annually in the United States, and costs billions of dollars for those who suffer from the disease. This disease is in fact a diverse group of disorders, which can originate in almost any tissue of the body. In addition, cancers may be generated by multiple mechanisms including pathogenic infections, mutations, and environmental insults (see, e.g., Pratt et al. (2005) Hum Pathol. 36(8): 861-70). The variety of cancer types and mechanisms of tumorigenesis add to the difficulty associated with treating a tumor, increasing the risk posed by the cancer to the patient's life and wellbeing.
Cancers manifest abnormal growth and the ability to move from an original site of growth to other tissues in the body (hereinafter termed “metastasis”), unlike most non-cancerous cells. These clinical manifestations are therefore used to diagnose cancer because they are applicable to all cancers. Additionally, a cancer diagnosis is made based on identifying cancer cells by their gross pathology through histological and microscopic inspection of the cells. Although the gross pathology of the cells can provide accurate diagnoses of the cells, the techniques used for such analysis are hampered by the time necessary to process the tissues and the skill of the technician analyzing the samples. These methodologies can lead to unnecessary delay in treating a growing tumor, thereby increasing the likelihood that a benign tumor will acquire metastatic characteristics. It is thus necessary to accurately diagnose potentially cancerous growths as quickly as possible to avoid the development of a potentially life threatening illness.
One potential method of increasing the speed and accuracy of cancer diagnoses is the examination of genes as markers for neoplastic potential. Recent advances in molecular biology have identified genes involved in cell cycle control, apoptosis, and metabolic regulation (see, e.g., Isoldi et al. (2005) Mini Rev. Med. Chem. 5(7): 685-95). Mutations in many of these genes have also been shown to increase the likelihood that a normal cell will progress to a malignant state (see, e.g., Soejima et al. (2005) Biochem. Cell Biol. 83(4): 429-37). For example, mutations in p53, which is a well-known tumor suppressor gene, have been associated with aberrant cell growth leading to neoplastic potential (see Li et al. (2005) World J. Gastroenterol. 11(19): 2998-3001). Many mutations can affect the levels of expression of certain genes in the neoplastic cells as compared to normal cells.
Typically, a gene will affect the phenotype of the cell through its expression at the protein level. Mutations in the coding sequence of the gene can alter its protein product in such a way that the protein does not perform its intended function appropriately. Some mutations, however, affect the levels of protein expressed in the cell without altering the functionality of the protein itself. Such mutations directly affect the phenotype of a cell by changing the delicate balance of protein expression in a cell. Therefore, an alteration in a gene's overall activity can be measured by determining the level of expression of the protein product of the gene in a cell.
There remains a need to identify an accurate and rapid means for diagnosing cancer in patients. Treatment efficacy would be improved by more efficient diagnoses of tissue samples. Furthermore, rapid diagnoses of cancerous tissues would allow clinicians to treat potential tumors prior to the metastasis of the cancer to other tissues of the body. Finally, a test that did not rely upon a particular technician's skill at identifying abnormal histological characteristics would improve the reliability of cancer diagnoses. There is, therefore, a need for new methods of diagnoses for cancer that are accurate, fast, and relatively easy to interpret.